Refactor with PMD, all rules

A violation remains - LawOfDemeter:   Potential violation of Law of Demeter (method chain calls)

./run.sh pmd -d /home/anit/work/codechallenge-java-pom/src/main/java/hackerrank/java/StringTokens.java -f text -R /home/anit/work/codechallenge-java-pom/.pmd --cache /tmp/codechallenge-pmd-analysis | less
 mvn test -Dtest=hackerranktest.java.StringTokensTest

Author: anitsh

src/main/java/hackerrank/java/StringToken.java

@@ -0,0 +1,39 @@
+package hackerrank.java;
+
+/**
+ * Clean token in string
+ */
+public class StringTokens {
+
+    /**
+     * String content to be cleaned
+     */
+    private final String sentence;
+
+    /**
+     *
+     * @return String
+     */
+    public String getSentence() {
+        return sentence;
+    }
+    /**
+     * Set string to be cleaned
+     * @param sentence
+     */
+    public StringTokens(final String sentence) {
+            this.sentence = sentence;
+    }
+
+    /**
+     * Filter tokens
+     *
+     * @return String
+     */
+    public String[] tokenFilter() {
+
+        return sentence == null || sentence.isEmpty() ?
+                new String[]{}
+        : sentence.trim().split("[,\\s\\'\\?\\_\\@\\!\\.]+");
+    }
+}

src/main/java/hackerrank/java/StringTokens.java

@@ -1,6 +1,6 @@
 package hackerranktest.java;
 
-import hackerrank.java.StringToken;
+import hackerrank.java.StringTokens;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
@@ -18,7 +18,7 @@ void givenASentencePrintWithoutTokens() {
         String given =  "He is a very very good boy, isn't he?";
         String expected =  "Heisaveryverygoodboyisnthe";
 
-        StringToken obj = new StringToken(given);
+        StringTokens obj = new StringTokens(given);
         String[] actualArr = obj.tokenFilter();
         String actual = String.join("", actualArr);
 
@@ -31,7 +31,7 @@ void givenAnEmptyStringPrintReturnEmptyString() {
         String given =  "";
         String expected =  "";
 
-        StringToken obj = new StringToken(given);
+        StringTokens obj = new StringTokens(given);
         String[] actualArr = obj.tokenFilter();
         String actual = String.join("", actualArr);